Reclosable fasteners for plastics bags and other containers

ABSTRACT

A reclosable fastener ( 10 ) comprising a male/female closure between a pair of opposed base members ( 18 ) has a single flange ( 16 ) for attachment of the closure to a web or film ( 34 ) on one only of the two base members. The fastener is attached initially to the film ( 34 ) by the single flange and then the fastener is additionally attached to the film ( 34 ) by heat and pressure applied in the region of attachment ribs ( 30 ) on the base members.

FIELD OF THE INVENTION

[0001] This invention relates to reclosable fasteners, otherwise knownas zippers, for plastics bags and other containers, and is particularlyconcerned with zippers intended to be applied to a film or web usingcross-web techniques.

BACKGROUND TO THE INVENTION

[0002] When a zipper strip is applied to a film or web, heat andpressure are applied to effect the welding of the zipper to a film orweb from which the bag or other container is to be made.

[0003] In order to secure the zipper to the film or web, the zipper isconventionally provided with a plurality of flanges on the twointerengageable members which together make up the fastener. The mostcommon practice is to provide four flanges, two on each member, in orderto seal these flanges to film or web material on each side of thezipper. However, some zippers are provided with only three flanges, andsome with only two. Sealing at the flanges is effected in order to keepheat and pressure away from the vulnerable male/female closure elements.However, it is a problem with such multi-flanged zippers that they tendto be bulky and do not easily deflect when used in cross-web procedures.

SUMMARY OF THE INVENTION

[0004] It is an object of the present invention to overcome thisproblem, by providing a zipper which is less bulky.

[0005] In accordance with the invention this is achieved by a reclosablefastener comprising a male/female closure between a pair of opposed basemembers, wherein a single flange for attachment of the closure to a webor film is provided on one only of the two base members.

[0006] The single flange is used to attach the zipper initially to theweb or film for subsequent sealing/welding of the zipper to the web orfilm in the region of the base members, by whatever means isappropriate.

BRIEF DESCRIPTION OF THE DRAWING

[0007] In order that the invention may be more fully understood, onepresently preferred embodiment of zipper in accordance with theinvention will now be described by way of example and with reference tothe accompanying drawing which is a schematic cross-sectional viewthrough the zipper.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0008] Referring to the drawing, there is shown a zipper, indicatedgenerally at 1o, comprising a first element 12 and a second element 14.The two elements 12 and 14 are generally the same as each other, apartfrom the tact that element 12 is provided with a single elongate flange16. Each element 12, 14 comprises a base member or body portion 18 withtwo upstanding legs 20 which terminate in hooks 22. The respective hooks22 of the two elements 12 and 14 are interengageable to make thereclosable fastener.

[0009] Each element 12, 14 also comprises an upstanding support post 24at one margin. The support post 24 is slightly longer than the hookedlegs 20, 22 so that it extends slightly beyond the tops of the legs. Theupper end surface 26 of each post 24 is tapered to provide an angledcontact surface. Facing each support post 24, on the opposing element,there is provided a heel portion 28, again at the margin. The surface ofeach heel portion 28 facing the respective post 24 is shaped, i.e.angled, to be complementary to the angled contact surface 26. As can beseen from the drawing, with this arrangement, the respective posts andheels nest with one another to provide a shape-locking configurationwhich tends to resist squashing or outward bending under vertical loads.The angled contact surfaces are able to absorb the welding pressure andmaintain their linear integrity, thus preventing the hooked legs 20, 22from being squashed or distorted.

[0010] In order to reduce the effects of the welding heat, each of theclosure elements 12 and 14 is provided with a pair of ribs 30 on theoutside face remote from the legs 20. The respective ribs 30 areprovided again at the margins of the closure, in alignment with theposts 24 and heel portions 28. The ribs 30 are provided by a thickeningof the material of which each of the two elements is composed. Becauseof the additional bulk provided by the ribs 30, they also contribute tothe resistance of the closure to deformation due to pressure. On eachrib 30 there is provided a layer 32 of a material which is ahigh-performance sealing/welding material or blend of materials, such asEVA for example. This facilitates the welding of the zipper to theadjacent web or film 34. The layers 32 are co-extruded with the closureelements 12 and 14.

[0011] The single long flange 16 which is part of element 12 is arrangedto face the inside of the bag or container. This single flange 16 isused for initial attachment to the film or web 34 as the zipper isapplied to the web by a cross-web technique. The provision of a singlelong flange provides increased internal strength to the bag by alteringthe angle at which the load in the bag acts against the zipper closure.The flange 16 is attached to the web or film 34 by the application ofheat and pressure from a sealing jaw or jaws (not shown). The flange 16could be provided on its surface adjacent to the web or film 34 withmaterial to facilitate the attachment of the flange to the web or film.

[0012] Although the invention has been described above in relation to aparticular design of zipper, it is to be understood that the inventionis not to be regarded as limited to this particular design of zipper,but can be applied to zippers of other designs and having otherconfigurations.

1. A reclosable fastener comprising a male/female closure between a pairof opposed base members, wherein a single flange for attachment of theclosure to a web or film is provided on one only of the two basemembers.
 2. A reclosable fastener as claimed in claim 1, in which thebase members include means to attach the fastener additionally to theweb or film.
 3. A reclosable fastener as claimed in claim 2, in whichthe base members are provided with ribs arranged to be attached to theweb or film.
 4. A reclosable fastener as claimed in claim 3, in whichthe ribs are positioned at the margins of the respective base members.5. A reclosable fastener as claimed in claim 3 or 4, in which a layer ofsealant material, is co-extruded on to each rib.